The present invention generally relates to automatic faucet systems, and more specifically, but not exclusively, concerns an automatic faucet sensor system that utilizes light polarization in order to enhance operational reliability.
Automatic faucets are increasingly being used in public restrooms and other commercial settings in order to minimize the spread of diseases and to provide greater convenience. Without physically contacting the faucet, a user is able to operate the faucet by simply placing an extremity, such as a hand, near the faucet. Upon detection of the user's hand, the automatic faucet supplies water so that the user is able to wash their hands. Once the user's hands are removed, the water supply is shut off.
Reliability in detection of the user's hands is always a concern. If the faucet is unable to detect the presence of a hand, the faucet may not turn on when desired. In contrast, objects that create a great deal of reflection can cause the faucet to run in an uncontrolled manner. Such reflective objects can include the sink, the surrounding environment, and even the stream of water supplied by the faucet. For example, once the water is turned on, the infrared signal from the automatic faucet may reflect off the water stream, thereby causing the faucet to run continuously. Moreover, such automatic faucet systems also have trouble in adapting to different background light levels. Numerous algorithms and techniques have been developed in order to reduce the number of false readings. However, such complicated detection techniques tend to increase the cost as well as reduce the reliability of the automatic faucet. Over time, the performance of these automatic faucets tends to deteriorate.
Other types of automatic faucet systems have been developed in attempt to alleviate the above-mentioned problems, but they only have achieved some limited success. For example, systems have been proposed that use polarized light in some manner for detecting false sensor readings. However, such systems have not been able to accurately detect objects because they fail to address a number of issues associated with light intensity. The intensity of light reflected from an object is based on a number of factors, like the distance of the object from the sensor as well as the reflectivity of the object. As should be appreciated, the intensity of light reflected from a distant object is less than the intensity of light reflected from the same object at closer distances. Ambient conditions along with the reflective properties of objects can also vary the intensity of light sensed. For instance, skin complexion and/or the amount dirt or other contaminants, such as paint, on the body part to be washed can vary from person to person. With these large numbers of factors, it is hard to distinguish between an object that is located far away from the sensor from those objects that have low reflectivity, and vice versa. Shiny object, such as jewelry or watches, that are highly reflective in nature can accidentally activate the automatic faucet, even when they are located relatively far away from the sensor. Conversely, dull or dirty objects, like hands covered with dirt, might not be able to activate the automatic faucet, although they are positioned directly in front of the faucet in close proximity to the sensor. Users sometimes experience frustration by not knowing if their hands are properly positioned to activate the automatic faucet, which in turn compounds the above-mentioned sensing difficulties.
Thus, there remains a need for improvement in this field.